Generally, a liquid crystal display (LCD) is a light receiving element which does not radiate light itself, thus it is usually used in conjunction with a back light unit (BLU) capable of uniformly increasing the illumination of a screen. In this respect, the BLU includes a light guide panel leading the refraction or the scattering of the light to convert an initial point or linear light source, such as a LED (light emitting diode), into a surface light source.
FIGS. 1A and 1B are a plan view and a sectional view of a conventional light guide panel, respectively.
With reference to FIGS. 1A and 1B, a light source 11, a kind of a fluorescent lamp such as the LED, is positioned at a lateral end of a light guide panel 10 and radiates light toward the light guide panel 10. A plurality of patterns 12 are formed on any one side of the light guide panel 10 to refract, scatter, and reflect the light radiated from the light source 11 to allow an intensity distribution of the light source 11 to be relatively uniform throughout the light guide panel 10 of the LCD, thereby an image is clearly displayed in the LCD.
The production of a mold on which the pattern 12 is formed is very important in the production of the light guide panel 10. With respect to the production of the mold, conventionally, a mold core is mechanically processed or etched to produce the mold on which the pattern is formed.
FIG. 2 schematically illustrates a mold used in a device for producing a light guide panel using a mold core according to a conventional technology.
Referring to FIG. 2, the mold used in the device for producing the light guide panel includes a heater 21, a gate 22, and the mold core 23.
A material used to produce the light guide panel is heated to a predetermined temperature by the heater 21, and transported through the narrow gate 22 into the mold core 23 to form the heated material into a predetermined shape in the mold core 23 according to a predetermined process such as an injection molding.
A detailed description of a conventional technology of producing a light guide panel using a mold core on which a pattern is formed is disclosed in Korean Utility Model Laid-Open Publication No. 20-0306881, entitled “a device for producing a light guide panel and a heat treatment device used in the same” filed by and allowed to this inventor.
However, the conventional technology of producing the light guide panel 10 using the mold core 23 on which the pattern is formed, as shown in FIG. 2, is disadvantageous in that it takes four to eight hours to replace the used mold core 23 with a new one, and operating conditions of an injection molding process must be optimized whenever the used mold core 23 is replaced with a new one.
Additionally, it takes 20 to 40 days to produce the mold core 23 on which the pattern is formed, thus the conventional technology is disadvantageous in terms of production time, manpower, and thus production costs.
Meanwhile, Korean Pat. Laid-Open Publication No. 2002-0015865, entitled “a device and a method of producing a light guide panel for a panel illuminator”, filed by this inventor discloses a method of producing the light guide panel using a stamper to avoid the disadvantages occurring in the conventional technology of producing the light guide panel using the mold core.
However, the method using the stamper is disadvantageous in that the stamper must be newly produced whenever the pattern is changed because it is impossible to conduct the pattern revision for the changed pattern. In other words, in the case of developing a new model of the light guide panel, the pattern revision is usually conducted ten times because of a design change or an error revision, but in the method of producing the light guide panel using the stamper, it is impossible to revise the pattern formed on the stamper, thus the stamper must be produced in conformity to the pattern revision. Hence, the method is insufficiently competitive in terms of production time, manpower, and thus production costs.